Mercedes has combined 3.5-litre, 4-valve V6 petrol engine with fully variable valve timing to implement "Direct Hybrid"--giving more importance to reduced fuel consumption. This was achieved with the help of spray-guided petrol direct injection. For the spray-guided combustion process, engineers developed a special piezo injection valve and a fuel system with a high pressure of 200 bar. One of the special feature of the process-- the stability of the injection spray is ensured by a special injection nozzle that opens to the outside and is triggered at ultra-high speeds by a piezo crystal. In this process, the fuel spray and the extremely rapid timing of the piezo nozzle allows the formation of a fuel-air mixture with the ideal flammability. The thermodynamic efficiency improves markedly and enables low fuel consumption with better engine performance.
The exhaust treatment for this layered direct injection process takes place in the double-stream exhaust system. The system also uses NOx trap system for reducing the nitrogen oxides along with the two bulkhead catalytic converters and controlled re-circulation of exhaust gas in each branch. It is thus possible to achieve extremely low exhaust emissions levels, which confirm to the current EU 4 exhaust emissions standards and the forthcoming EURO 5 limit.
Among all these features, the standout feature of the "Direct Hybrid" is the high-torque electric motor built into the engine. While engineers achieved a highly efficient petrol engine that is low on emissions, the combination of electric motor turns the whole set-up into a mild hybrid.
Besides, the fact that the electric motor is fitted between the engine and the 7G- TRONIC automatic transmission`s converter saves space. Depending on the driving situation, the motor functions as a starter or a generator. This is particularly useful in the heavy traffic of an urban area, as it makes it easy to create an automatic stop-and-go transmission that alone can save three to six per cent of fuel under these conditions. A quick touch of the accelerator and the electric motor smoothly brings the engine back to life with the electric motor supplying a maximum of 250 Nm torque to the drive power for the start. It thus provides optimal support for the combustion engine, which as a consequence of its operating principle, first builds up its torque as the revs increase. The combination of motor and engine boosts the maximum available torque to 395 Nm and makes the vehicle`s starting characteristics powerful.
The real potential of electric motor comes into play in heavy stop-and-go traffic. In spite of its dynamic acceleration (0-100 kph in 7.5seconds) the "Direct Hybrid" uses just 8.3 litres of petrol per 100 km in the European Driving Cycle. Hence, Compared with its predecessor model, the 5350 V6 (W 220), the power has shot up by 19 per cent and the consumption has gone down by an impressive 25 per cent.
Furthermore, by reversing its function, the electric motor can also regain a portion of the vehicle`s kinetic energy during phases of coasting without acceleration and when engaged in regenerative braking. This energy is stored in a new type of rechargeable high-performance battery using lithium ions. Energy storage devices of this type are distinguished by their high power density, and can charge and discharge electrical energy extremely rapidly.
While performance of Mercedes-Benz car are on top, Mercedes-Benz is also investigating the use of high-performance capacitors known as ultracaps for boosting its fuel saving capability, depending on the application profile.
Working on the same lines of the "Direct Hybrid" petrol variant, the "Bluetec Hybrid", introduced by Mercedes-Benz, uses an additional 8.2 bhp electric motor, which serves both as starter and as starting booster. It can also be used for regenerating power from kinetic energy. The basic attracting feature of the "Bluetec Hybrid" is the 3-litre V6 diesel engine, a variant of the 320 CDI with 235 bhp of output and a maximum torque of 540 Nm that is already available at between 1,600 and 2,400 rpm.
The "Bluetec Hybrid", also goes a step further to make maximum use of emissions reduction technology with diesel`s typical advantages of economy and agility and the consumption technology of a mild hybrid. This new innovative technology can achieve consumption figures of 7.7 litres per 100km in the European Driving Cycle.
Hence, when comparison is drawn to the earlier S-Class, which according to Mercedes engineers was unusually economical, the Bluetec Hybrid represents a further saving of 20 per cent for comparable power and torque. Driving pleasure, economy and ecology are the unmatchable features of this concept.
The Bluetec technology, involving selective catalytic reduction (SCR), is already fitted to more than 5000 Mercedes Benz Actros and Axor truck range. The vehicles thus meet the Euro 5 emission standards reducing the emission of nitrogen oxides by around 80 per cent. The SCR works by measured addition of "AdBlue" - an aqueous carbamide solution - into the exhaust line. The AdBlue must be metered precisely according to the driving situation in order to always achieve the maximum catalytic converter conversion rates. This reacts with the nitrogen oxides in the catalytic converter to form ammonia (NH3) as an intermediate product, which then is converted into the harmless natural products of water and nitrogen
A 22-litre tank has been built into the spare wheel well of the S-Class in order to ensure fit well within the NOx exhaust emissions limits over the normal service interval. Average AdBlue consumption is around O.I-litre per 100km. If in any case, the supply run out before the next service, a signal in the instrument cluster alters the driver to visit a service station in plenty of time. Hence, this tank is sufficient for the driving distance between two service intervals and the service personnel simply fill the tank up automatically when the car goes in for its next service giving customer zero worry about the metering of the AdBlue.